1. The problem statement, all variables and given/known data 1) Why, in general, do brittle materials not acheive their theoretical tensile strengths? 2) Why, in general, do ductile materials not acheive their theoretical shear strengths? 2. Relevant equations None needed. Wordy answer. 3. The attempt at a solution Something to do with the stress intensity factor / defects for brittle materials?? Thanks.